In February a critical vulnerability was found in Adobe Reader/Writer 9 and earlier versions. This vulnerability would cause the application to crash and could potentially allow an attacker to take control of the affected system. There is now a virus out that exploits this and there are reports that this issue is being exploited.
There are updates available for version 7 though 9. Adobe recommend that you don’t update older versions but go straight to V9.1. There are some rare instances where an older version is required to run other 3rd party software. Please talk to your Account Manager or engineer before proceeding to update to this version.
Read more about this issue 
Here